The present invention relates generally to apparatus and methods for segmenting a tubular member into two conduits, primarily for conducting well treating operations; more particularly, it relates to a baffle system and method for its use in such well treating operations.
It has become common practice in the completion and workover of oil and gas wells to treat a formation by injecting fluids through perforations in a casing set is a well bore and into the formation. For example, acids may be injected to promote production (acidizing), surfactants may be injected to lower interfacial tension, alter formation wettability and break emulsions, cations or polymers may be injected to control clay swelling, and water or brine may be injected to pressurize a formation.
There are also occasions where the resident well bore fluid must be removed simply to facilitate operations. For example, in perforating the well it is desirable to evacuate the tubing to establish a lower pressure in the well bore than in the formation. This "underbalanced" perforating technique cleans the perforations by causing debris from the perforating gun and other sources to be blown out of the perforations and into the well bore where this debris can be carried to the surface.
The well bore is often filled with formation fluids or fluids left over from previous operations, hampering further injection operations. One common method of removing these fluids prior to injection operations is to pump them ahead of a treating fluid into the producing formation (the "bull-head" technique). Although this method has an advantage in that no additional equipment is required, it also has the substantial disadvantage that fluids potentially harmful to the formation must be pumped into the formation.
Well bore fluids for both injection and perforating operations may also be removed by gas lifting the fluids to the surface with nitrogen and a coiled tubing unit. In this operation, a flexible metal tube from a coil is lowered into the well bore inside existing tubing. Once the end of the tube is at the desired depth, a displacing fluid, usually nitrogen, is injected into the well bore through the tube to displace the well bore fluid up the annulus between the injection tube and the well bore tubing. While this method removes the unwanted well bore fluids and minimizes potential damage to the formation from the harmful components of the well bore fluid, it also requires that additional equipment be brought on site and that a nitrogen source and compressor be used in displacing the well bore fluids.
Downhole information cannot easily be gathered during the injection operations of the prior art methods. Thus, it is difficult to analyze the well treating operation as it progresses. For example, changing formation permeability during the treatment cannot be readily measured by the prior art methods except through surface pressure measurements. Uncertainties in the average fluid density within the well bore plus friction pressure drops during the injection operation make the observed surface pressures less reliable than bottom hole pressure measurements.
It is, therefore, an object of the present invention to provide apparatus and methods for conducting well treating operations whereby the well bore fluids can be displaced from the well bore with minimum potential damage to the producing formation.
It is a further object of the present invention to provide apparatus and methods for conducting well treating operations whereby only a small amount of additional equipment is required on site to perform such operations.
It is a still further object of the present invention to provide apparatus and methods which allow downhole measurements to be made during the operations to facilitate the analysis of the treating operations as they progress.